JP2021155932A - Steel-framed reinforced concrete structure and construction method thereof - Google Patents

Abstract

To provide a novel technology of improving fixation force of reinforcements arranged by penetrating through hole parts of steel frames, in a steel-framed reinforced concrete structure.SOLUTION: A through-type SRC bridge 2 being a steel-framed reinforced concrete structure has an H-section steel 10 (steel frame) having a web (steel plate) having hole parts 16, annular members 18 arranged on the steel plate to surround the hole parts 16, and deformed bars 62 penetrating through the hole parts 16. In the through-type SRC bridge 2, a concrete part 14 is placed to bury the H-section steel 10, the annular members 18 and the deformed bars 62.SELECTED DRAWING: Figure 1

Description

The present invention relates to a steel-framed reinforced concrete structure and the like.

Fixing of reinforcing bar and concrete in a reinforced concrete structure is (1) fixing by adhesion to concrete, (2) anchor effect that resists pulling out in the axial direction of the reinforcing bar by changing the shape of the tip of the reinforcing bar, (3) added to the reinforcing bar. It can be roughly divided into mechanical fixing by mounting members.

(2) Examples of changing the shape of the tip of the reinforcing bar include a method of bending the tip of the reinforcing bar into a U-shape or a J-shape, and a method of hot-installing the end of the reinforcing bar to form an enlarged diameter portion. It is known (see, for example, Patent Document 1). Further, as an example of (3) attaching an additional member to the reinforcing bar, a method of attaching an anchor metal fitting is known (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2000-257209 JP-A-2018-080495

Among the reinforced concrete structures, in a steel reinforced concrete (SRC: Steel Reinforced Concrete) structure (hereinafter, SRC structure) that uses a steel frame as a structure, there is a case where it is desired to make a hole in a steel plate of the steel frame to allow the reinforcing bar to penetrate. I want to fix the reinforcing bar to be penetrated and concrete, but because it is not possible to pass through the hole provided in the steel plate, the reinforcing bar whose tip is bent in a U shape or J shape in advance, or the reinforcing bar in which the enlarged diameter part is formed in advance, In some cases, it is not possible to use reinforcing bars with additional members attached in advance. When using straight reinforcing bars in such cases, it is necessary to obtain a sufficient fixing length. However, there are cases where a sufficient fixing length cannot be obtained due to interference between the members, and there are cases where it is desired to avoid an increase in construction cost and weight due to the lengthening of the fixing length.

The present invention has been devised as an object of providing a new technique for improving the fixing force of a steel bar inserted through a hole provided in a steel frame in a steel-framed reinforced concrete structure (SRC structure). Is.

The first invention for solving the above-mentioned problems is a steel frame having a steel plate provided with a hole, an annular or spiral member arranged on the steel plate so as to surround the hole, and the hole. It is a steel-framed reinforced concrete structure (SRC structure) including a deformed reinforcing bar inserted into a portion, and the steel frame, the member, and the deformed reinforcing bar are embedded in concrete.

Assuming the configuration of the first invention, when a pulling force acts on the deformed reinforcing bar embedded in concrete, focusing on the downstream side in the pulling direction with the steel plate having a hole as a boundary, the nominal diameter portion of the deformed reinforcing bar A combined force is generated between the first drag force on the steel surface (drag force along the tensile direction due to the adhesive force with concrete) and the second drag force (bearing resistance) generated on the side surface of the convex portion of the deformed reinforcing bar in the tensile direction. It is considered that the surface of the steel sheet on the downstream side in the tensile direction receives this deformed synthetic force.

Here, assuming a virtual cone with the deformed reinforcing bar as the axis and the contact surface with the steel plate as the bottom, the synthetic force breaks the concrete around the deformed reinforcing bar by opening the bottom surface of the virtual cone in a trumpet shape. Acts as a spreading force. However, in the first invention, an annular or spiral member is arranged on the steel plate so as to surround the hole. Since the member is also embedded in concrete, an annular or spiral member is embedded in the bottom surface of the virtual cone.

Therefore, when the expanding force acts on the virtual cone, the annular or spiral member resists the expanding force, and the fracture strength of the virtual cone is improved as compared with the configuration in which the annular or spiral member is not provided. Therefore, according to the first invention, the annular or spiral member can improve the fixing force of the reinforcing bar arranged through the hole of the steel frame.

The second invention is the steel-framed reinforced concrete structure of the first invention, in which the member is an annular shape.

According to the second invention, by making the shape of the annular or spiral member annular, a weak portion in a specific direction is not generated, so that the member produces a strong drag force. Therefore, it is possible to effectively improve the fixing force of the reinforcing bar arranged by inserting the hole of the steel frame.

The third invention is the steel-framed reinforced concrete structure of the second invention, in which a plurality of the members having different sizes are arranged concentrically.

According to the third invention, by providing the annular or spiral member in multiple stages, the strength of the bottom surface of the virtual cone is further increased, and the fixing force of the reinforcing bar arranged through the hole of the steel frame is further increased. It can be effectively improved.

The annular or spiral member is not limited to an annular member. As a fourth invention, the steel-framed reinforced concrete structure of the first invention, in which the member is spiral, can also be constructed.

A fifth invention is a step of arranging an annular or spiral member so as to surround the hole on the steel frame of a steel frame having a steel plate provided with a hole, and inserting a deformed reinforcing bar into the hole. It is a method of constructing a steel-framed reinforced concrete structure including a step and a step of placing concrete around the steel frame, the member and the deformed reinforcing bar.

According to the fifth invention, a steel-framed reinforced concrete structure (SRC structure) having the same effect as that of the first invention can be constructed.

A cross-sectional view of a lower road type SRC bridge which is an example of a steel-framed reinforced concrete structure. The figure which showed the hole part of H-shaped steel, the annulus member, and the deformed reinforcing bar of the floor slab extracted. The figure for demonstrating the drag force against the pull-out force which concerns on a deformed reinforcing bar. The figure for demonstrating the modification using the spiral member which substitutes for an annulus member.

Hereinafter, embodiments of the present invention will be described, but it goes without saying that the embodiments to which the present invention can be applied are not limited to the following embodiments. Further, each figure shows an orthogonal XYZ axes indicating a common direction.

FIG. 1 is a cross-sectional view of a lower road type SRC bridge as an embodiment of a steel-framed reinforced concrete structure to which the present invention is applied. The longitudinal direction of the girder is the Z-axis direction (front / back direction toward FIG. 1) of the orthogonal XYZ axes in the drawing.

The lower road type SRC bridge 2 has an SRC structure girder portion 4 and an RC structure floor slab 6 (slab).

The girder portion 4 has an H-shaped steel 10, a reinforcing bar 12 surrounding the girder portion 4, and a concrete portion 14 cast so as to bury them. The H-section steel 10 is provided with holes 16 in the web (steel plate portion in the vertical direction in FIG. 1), and a plurality of H-shaped steels 10 having different diameters are provided on the outer peripheral portion of the hole portion 16 and the web side surface on the tip side of the reinforcing bar 62. 18 (18a, 18b) of the ring member 18 (18a, 18b) of the above is attached.

The concrete portion 14 of the girder portion 4 is cast integrally with the concrete to be filled in the floor slab 6.

The diameter of the hole 16 is set to be larger than the maximum diameter of the deformed reinforcing bar 62 of the deck 6. Further, the diameter of the hole portion 16 does not have to be large enough to allow a reinforcing bar having an enlarged diameter portion at the tip portion or a reinforcing bar having a hook-shaped tip to be inserted.

FIG. 2 is a view showing the holes 16 of the H-section steel 10, the annulus members 18 (18a, 18b), and the deformed reinforcing bars 62 of the deck 6 extracted, and the longitudinal direction of the girder is in the left-right direction. It is a figure shown as. Reinforcing bars 12 and concrete portions 14 are not shown. The annulus member 18 is shaded for easy identification.

The annulus members 18 (18a, 18b) are made, for example, by cutting out from a steel plate material or by slicing from a circular pipe material, and are attached to the web of the H-shaped steel 10 by adhesion. The ring member 18 is preferably a plurality of members having different diameters arranged concentrically, but may be a single number. The gaps inside and outside the plurality of ring members 18 are set at appropriate intervals so that the concrete is sufficiently filled. Further, the height of the annulus member 18 can be set as appropriate.

In the construction of the lower road type SRC bridge 2, (1) the ring member 18 is arranged so as to surround the hole 16 on the web (steel plate) of the H-shaped steel 10 (steel frame) provided with the hole 16. 1st step, (2) 2nd step of inserting the deformed reinforcing bar 62 into the hole 16, (3) 3rd step of placing concrete around the H-shaped steel 10 (steel frame), the annular member 18 and the deformed reinforcing bar 62. , And so on.

FIG. 3 is a diagram for explaining a drag force against a pulling force of the deformed reinforcing bar 62.
It is assumed that the pulling force F acts on the deformed reinforcing bar 62 embedded in the concrete portion 14. Focusing on the downstream side in the pulling direction (left direction in FIG. 3) with the web (steel plate) of the H-shaped steel 10 as a boundary, along the tensile direction due to the adhesive force with concrete on the steel surface of the nominal diameter portion of the deformed reinforcing bar 62. A compressive force f (fine dotted arrow in the figure) acts on the concrete portion 14 by the first resistance force and the second resistance force as a bearing force generated on the side surface of the convex portion of the deformed reinforcing bar 62 facing the tensile direction. , The upstream side of the web of the H-beam 10 receives this.

Here, in the concrete portion 14 around the deformed reinforcing bar 62 on the downstream side of the web of the H-shaped steel 10, a virtual cone 9 having the deformed reinforcing bar 62 as the axis and the contact surface of the H-shaped steel 10 with the web as the bottom (in the figure). Assuming that the one-point chain line indicates the bus of the virtual cone 9), the compressive force f acts as an expanding force that breaks the bottom surface of the virtual cone 9 by opening it in a trumpet shape. However, the annulus members 18 (18a, 18b) are arranged so as to surround the hole 16. Since the annular member 18 (18a, 18b) is also embedded in the concrete portion 14, the annular member 18 (18a, 18b) is installed on the bottom surface of the virtual cone 9.

Therefore, when the expanding force acts on the virtual cone 9, the annular member 18 (18a, 18b) resists the expanding force, and the virtual cone is more than the configuration without the annular member 18 (18a, 18b). The breaking strength of the shape 9 is improved. Therefore, the fixing force of the reinforcing bar arranged through the hole of the steel frame is improved.

[Modification example]
Although an example of the embodiment to which the present invention is applied has been described above, the embodiment to which the present invention can be applied is not limited to the above embodiment, and the components may be omitted, added, or changed as appropriate. can.

For example, in the above embodiment, the web of the H-shaped steel 10 is exemplified as the position where the hole portion 16 is provided, but the hole portion 16 may be provided at another portion of the H-shaped steel 10. Further, the steel plate provided with the hole 16 is not limited to the H-shaped steel 10, and may be a steel frame having another shape.

Further, for example, the annular member 18 may have another shape as long as a portion that partially protrudes from the steel plate surface can be formed around the hole portion 16. For example, the annulus member 18 has an annulus in the front view (view in the hole axis direction of the hole portion 16), but the shape in the front view may be a polygon. Further, as shown in FIG. 4, as an alternative member to the annular member 18, the shape of the front view may be a spiral member 18B.

2 ... Underpass type SRC bridge 4 ... Girder part 6 ... Floor slab 9 ... Virtual conical shape 10 ... H-shaped steel 12 ... Reinforcing bar 14 ... Concrete part 16 ... Hole part 18 ... Ring member 18B ... Swirl member 19 ... Convex part 62 ... Deformed reinforcing bar F ... Pulling force L ... Fixing length f ... Compressive force

Claims (5)

A steel frame having a steel plate with holes and
An annular or spiral member arranged on the steel plate so as to surround the hole,
The deformed reinforcing bar inserted into the hole and
A steel-framed reinforced concrete structure in which the steel frame, the member, and the deformed reinforcing bar are embedded in concrete. The member is annular,
The steel-framed reinforced concrete structure according to claim 1. The steel-framed reinforced concrete structure according to claim 2, wherein a plurality of the members having different sizes are arranged concentrically. The member has a spiral shape.
The steel-framed reinforced concrete structure according to claim 1. A step of arranging an annular or spiral member on the steel plate having a steel plate provided with holes so as to surround the holes.
The process of inserting the deformed reinforcing bar into the hole and
The step of placing concrete around the steel frame, the member, and the deformed reinforcing bar, and
How to build a steel reinforced concrete structure including.

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